Human Factors vs. Bugs – Somebody stop my Toyota!

In one of my courses this year I had students talk about the kinds of human factors problems they had run across when using computers. There were a number of great anecdotes, but one thing that interested me was the difficulty they had discerning the difference between a software bug and a human factors problem. For example, one student complained that if they clicked on a certain button in a program, it crashed the computer.

It was interesting trying to explain the difference. I basically said that a bug is an unintentional effect while a usability problem is due to some misunderstanding of how humans could or should use a system. This isn’t perfect; some human factors problems come from “bugs” that went undiagnosed during development. Generally, I think bugs are not representative of any misunderstanding of human abilities or limitations.

The difference between human factors problems and bugs is about to become very important for Toyota. These are excerpts from a recent ABC news story:

Refusing to accept the explanation of Toyota and the federal government, hundreds of Toyota owners are in rebellion after a series of accidents caused by what they call “runaway cars.” Safety analysts found an estimated 2000 cases in which owners of Toyota cars including Camry, Prius and Lexus, reported that their cars surged without warning up to speeds of 100 miles per hour.

…

Toyota says the incidents are caused by floor mats becoming stuck under gas pedals, but owners say that’s not what happened to them.

…

“I’m absolutely certain that in my situation, it was not the floor mats,” Elizabeth James told ABC News. She was driving her Toyota Prius outside Denver, CO when she says it suddenly shot up to 90 miles an hour, even though her foot was on the brake and not the gas pedal. “I kept going faster and faster,” James said. “And all of a sudden& my foot was pressing on the brake super, super hard and I wasn’t slowing down.” James and some other Toyota owners suspect the accidents have been caused by some kind of glitch in the electronic computer system used in Toyotas that controls the throttle.

…

The National Highway Traffic Safety Administration has done six separate investigations of such acceleration surges in Toyotas since 2003 and found no defect in Toyota’s electronics.

…

“Toyota has announced a safety recall involving 3.8 million vehicles in which the accelerator pedal may become stuck at high vehicle speeds due to interference by the driver’s side floor mat, which is obviously a very dangerous situation.

On the human factors side, we have a known issue with the floormats (indeed, I’ve had to pull my Matrix floormat back for years as it creeps forward.) We also have prior incidents of personsmistaking the accelerator for the brake. On the bug side we have a car with a great deal of control given to electronics. Frankly, Toyota loses either way.

The interesting part is how the drivers believe it would be more Toyota’s fault if there is a “bug” in the electronics than if the problem has to do with human factors design. We appear to feel more control over a human factors issue, even when it is beyond our control, than we do with a software bug.

This attitude can be seen over in a Consumerist post of a 911 call by a family with a floormat-stuck gas pedal. (I don’t suggest listening to the call .) Read the comments instead, they include:

“Maybe I’m missing something, but couldn’t they just have turned the engine off?”

“It is sad but the driver had the ability to put the car in neutral or turn off the engine off at any point.”

“maybe it was the way I was raised, but I understand the concept of putting a car in neutral, or stepping on the clutch, or shutting the engine off… I’m not trying to be crass, but I feel like everyone should understand these concepts before driving.”

and (wow) –

“I’m gonna come out and say it: It was his fault. His failure, as the driver, to keep his head about him in an unexpected emergency was the #1 cause of the death of his family. The fact that he called 911 is inexplicable, and the fact that some posters on this board call that an example of “having his wits” really makes me question their basic intelligence level. The fact that this story will tarnish Toyota, an otherwise crap car maker, is sad. Sometimes, shit happens. You can place blame, sue, complain, etc. – but if you aren’t sharp enough and alert enough at the time to do the right thing, it doesn’t matter who’s to blame.”